1. Field of the Invention
Embodiments of the present invention relate to a semiconductor physical quantity sensor device.
2. Description of the Related Art
Filter circuits for blocking exogenous electromagnetic wave noise are mounted inside integrated circuit (IC) chips as a measure against electromagnetic wave noise in semiconductor physical quantity sensor device such as a pressure sensor apparatus. For example, in an IC chip used in automobiles, etc., a capacitor-resistor (CR) filter made up of a capacitor and a resistor (hereinafter, filter resistor) has a single-stage configuration or a multistage configuration like a quadratic filter and is connected to power source wiring or sensor output wiring of the integrated circuit.
A configuration of a conventional semiconductor physical quantity sensor device will be described by taking, as an example, a case in which a CR filter is connected to power source wiring in a single-stage configuration. FIG. 14 is a circuit diagram of an example of a conventional semiconductor physical quantity sensor device. The conventional semiconductor physical quantity sensor device depicted in FIG. 14 includes internal circuits such as a sensor unit 101, an operational amplifier 102, a characteristic correction circuit 103, and a reference voltage circuit 104 connected in parallel between a power source terminal (power source pad) 111 and a ground terminal (grounding pad) 113. Source voltage Vcc is applied to the power source terminal 111 from an external source. Ground voltage GND is applied to the ground terminal 113. An output terminal 112 outputs to an external destination, output voltage Vout from the operational amplifier 102.
A CR filter 105 made up of a capacitor 106 and a filter resistor 107 is connected in a single-stage configuration to power source wiring S1 connecting the internal circuits and the power source terminal 111. The filter resistor 107 is connected to the power source wiring S1. The capacitor 106 has a positive electrode connected between the filter resistor 107 and the operational amplifier 102 and a negative electrode connected between the operational amplifier 102 and the ground terminal 113. Reference character C1 denotes the capacitance of the capacitor 106. The CR filter 105 acts as a low-pass filter removing radio noise input to the power source terminal 111 and suppresses variations in potential in the power source wiring S1 due to electromagnetic noise.
Among semiconductor physical quantity sensor devices having a CR filter as described above, a device has been proposed in which the lengths and widths of wiring are selected to satisfy a relational equation [R1/Rf×100<25], where Rf is a resistance value of the resistor making up the CR filter of the wiring connecting the internal circuits and the power source pad, and R1 is a parasitic resistance component of the wiring from the power source pad to the internal circuits (for example, refer to Japanese Laid-Open Patent Publication No. 2006-310658). In Japanese Laid-Open Patent Publication No. 2006-310658, the parasitic resistance component R1 is set to 25% or less relative to the resistance value Rf of the resistor making up the CR filter so as to improve the performance of the CR filter.
Another semiconductor physical quantity sensor device having a CR filter has been proposed that has separate ground wiring of differing configurations respectively for circuit reference voltage and for a noise filter. The ground wiring is connected via a grounding pad to a bonding wire to form a single-point ground (for example, refer to Japanese Laid-Open Patent Publication No. 2006-162421). In Japanese Laid-Open Patent Publication No. 2006-162421, voltage variations are prevented in the ground wiring for the circuit reference voltage when high-frequency noise is applied/injected to a sensor chip (IC chip), so as to improve noise immunity.
Performance qualities important for semiconductor physical quantity sensor devices include a wide sensor-chip output voltage range in addition to the high noise immunity described above. For example, rail-to-rail output that enables the sensor-chip output voltage range defined substantially from a lower limit value (ground voltage GND) to an upper limit value (source voltage Vcc) is ideal. Various push-pull output type operational amplifiers have been proposed as rail-to-rail output operational amplifiers (for example, refer to Japanese Laid-Open Patent Publication No. 2004-222015).
Additionally, important indexes representative of the performance of semiconductor physical quantity sensor devices include non-linearity. Non-linearity is an index indicative of whether an amplitude Y of a converted/output signal is linear (first-order) with respect to an amplitude X of a physical quantity applied to the sensor chip. This means quantifying the extent of divergence of actual output voltage Vout having a curve of the second order, from an ideal linear equation Y=aX+b (a and b are constants) of the output characteristics of the sensor chip. The ideal value of the output characteristics of the sensor chip represents a state in which non-linearity error is zero, i.e., a state without divergence from the ideal linear equation.
For a semiconductor physical quantity sensor device configured to adjust the non-linearity of the output characteristics of the sensor chip, an apparatus has been proposed that includes a voltage amplifying unit that amplifies and outputs the output from a sensor element unit for pressure, and an output voltage feedback unit that feeds back the output voltage of the voltage amplifying unit as a reference power source voltage so as to give non-linear characteristics to the output voltage of the voltage amplifying unit with respect to pressure (for example, refer to Japanese Laid-Open Patent Publication No. 2003-139638).